1. Field of the Invention
This invention relates generally to cleansing bars, and more particularly to mild cleansing bars having substantial lather, low mush and wear rates.
2. The Related Art
Generally mild toilet bars are formulated with synthetic detergents (syndets) that replace soap to a large extent. Synthetic detergent or syndet toilet bars formulated with acyl isethionates or esterified fatty isethionates have found. considerable use as mild cleansing bars with excellent skin feel, lather, and slip properties but such bars may be difficult to process or have the potential to exhibit undesirable mush levels and high rates of wear unless formulated with substantial levels of structurants such as soap. It would be highly desirable to create a syndet bar based upon mild acyl isethionates that maintains its attractive skin feel properties, that is amenable to processing and that reduces the negative aspects of high mush levels and high rates of wear without the need for high levels of structurants, such as soap.
The use of toilet bars manufactured with DEFI (directly esterified fatty isethionate) technology particularly sodium isethionate, as a reactant with coco fatty acid has been disclosed in e.g. U.S. Pat. No. 2,894,912 issued to Geitz on Jul. 14, 1959. The use of “DEFI-like” mild surfactants through incorporation of alternative reactants to replace sodium isethionate (alkali metal isethionates or AIT) has been disclosed. U.S. Pat. No. 6,562,874 issued to Ilardi et. al., on May 13, 2003 teach the substitution of AIT with specific alcohols as well as fatty acid replacement with alternative carboxylic acids etc. and other formula modifications to enhance mildness. U.S. Pat. No. 3,376,229 issued to Haass and Lamberti on Apr. 2, 1968 disclose the use of AIT's to be used as firming agents. Tokosh and Cahn (U.S. Pat. No. 4,180,470 issued on Dec. 25, 1979) teach the use of alkoxy-hydroxy propane sulfonates as firming agents for bars.
The use of acyl isethionates with divalent metal counterions (e.g. Mg, Ca, etc.) has also been previously disclosed. For example, U.S. Pat. No. 5,994,289 issued to Nestler on Nov. 30, 1999 teaches the use of surfactant mixture containing acyl isethionates with mixed counterions, including ammonium, alkali metal and/or alkaline-earth metals. U.S. Pat. No. 6,559,110 issued to Lopes on May 6, 2003 discloses a syndet bar comprising 0.1 to 95% by weight of at least one anionic surfactant such as acyl isethionate having a calcium or magnesium salt. U.S. Pat. No. 6,046,147 issued to Cassady et al. on Apr. 4, 2000 teaches a bar composition comprising 20 to 30% weight of acyl isethionate having a cation of an alkali earth metal and alkyl polyglycoside. U.S. Pat. No. 4,663,070 issued to Dobrovolny et al. on May 5, 1987 teaches a toilet bar comprising 2 to 45% acyl isethionate ester salt having a cation of ammonium, potassium, sodium, calcium or magnesium.
Unexpectedly it has been discovered that divalent metal isethionate(s) when used at a certain ratio and/or in combination with mono-valent C8-C18 isethionate(s) (such as e.g. cocoyl isethionate) form a complex with the DEFI reaction mixture as described below with a Krafft point comparable to that of mono-valent C8-C18 isethionate(s). Furthermore it was unexpectedly discovered that magnesium acyl isethionate forms a higher Krafft point complex then calcium acyl isethionate with the same Defi Reaction mixture.
When used in specific ratio ranges, these acyl isethionates provide a toilet bar that is mild, produces substantial lather, is more resistant to wear, and has less mush compared to prior art toilet bars composed of monovalent metal cocoyl isethionates alone. This is surprising since the art teaches that bars containing diacyl isethionates are generally less soluble than monoacyl isethionates and would therefore be expected to produce less lather during use when formulated into a toilet bar. Such toilet bars may also be processed within commercially acceptable parameters and with processing equipment typically used to manufacture toilet bars.